Data acquisition for long-term monitoring of physiological signals and video signals of patients is exceedingly valuable in the current medical environment.
This invention relates to obtaining, storing, and analyzing video and analog signals. In particular the invention is concerned with the simultaneous processing of such signals.
A need exists for acquisition of dynamic video images of physiological processes of a patient simultaneously with electrophysiological signals of the patients.
Correlation of both the video signals and the physiological signals at high temporal resolution is valuable. The rapid computer retrieval of these signals, is also a requirement.
Synchronous video and analog signal acquisition are required for visual determination of sleep state, body or limb position, or somatic activity together with collection of electroencephalographic, electrocardiographic, respiratory or electromyographic activity. Examination of cellular optical properties that are associated with unique electrophysiological patterns is also a consideration.
Concurrent video and analog recordings are useful for evaluation of electrophysiological signals associated with sleep disorders, simultaneous monitoring of seizure activity and limb movements, and comparison of electrophysiological signals with changes in optical properties of neural tissue.
A need also exists for concurrent recording of a hundred or more channels of EEG.
Typically, video images and physiological signals are acquired and stored on separate media with common synchronizing signals. Often physiological data are captured in digital format, with video data stored on analog media. During analysis, the signals are temporally aligned using synchronizing pulses. However, processing data with analog technology is cumbersome and time consuming. If frame accuracy is required, synchronization demands specialized video recorders. Even if video data are stored digitally, synchronizing digitized physiological signals with images is often difficult.
An ideal physiological monitoring system for acquiring data, particularly from sleeping infants or epileptic subjects, would have facilities for collecting multiple channels of physiological signals gathered at high temporal resolution. The system would also store video indications of body position, movements, or other somatomotor characteristics. Such characteristics are usually noted by an observer using handwritten notes or specially-coded signals.
Observer-based encoding methods lack detailed description, suffer from errors introduced by fatigue and observational lapses, and lack high temporal resolution. Behavioral measurements should minimally interfere with normal physiological functions, and should provide near-instantaneous access to both video and physiological data on a computer-readable format for analysis.
The need also exists for a video system to monitor infants at risk for the sudden infant death syndrome (SIDS). Information pertaining to body position during the night, extent of body covering, and patterns of movements are of special interest. At the same time, a need exists to gather multiple channels of physiological data at high temporal resolution. Multiple channels are required for adequate identification of state and to appropriately identify interactions between several physiological systems which may fail in SIDS victims.
Recording of epileptic patients would also greatly benefit by acquisition of video images of ictal episodes simultaneously with physiological signal acquisition.
The classical procedure for simultaneous video and physiological signal acquisition usually stores video images on videotape media, and physiological signals on other media.
In many studies, the physiological and video signals are stored on separate tapes. The two signal sources are then coordinated by using a synchronizing code. However, integration of physiological signals with video data requires substantial manual intervention which is costly, frequently not accurately time-synchronized, and exceptionally unwieldy to use.
Occasionally, signals from a video camera viewing the subject is mixed with signals from a second video camera viewing the polygraph record. The combined video signals are displayed on a split screen, and video-taped for correlation of image and electrophysiological events. Procedures which use videotape as a primary medium for storage of video signals have several handicaps. Such storage is typically in a non-computer retrievable format, and the physiological signals lack sufficient resolution for analysis.
The known systems for obtaining and recording signals from different sources and rendering them recoverable with a video signal suffer limitations.
A need clearly exists for improved system to achieve these objectives.